Tilt controls for chairs

Abstract

A tilt mechanism for a chair includes rotary stop means defining a plurality of selectable tilted positions of the chair seat/back. In another aspect, an anti kick-back feature is provided based. The mechanism includes upper and lower housing parts and a cushioning spring that normally maintains the parts in a rest position with respect to one another while allowing the mechanism to tilt. A further aspect of the invention provides an improved spring tension control that allows the spring to be installed and removed in a fully relaxed condition so that no special tools are required.

1. A tilt mechanism for a chair comprising:
 upper and lower housing parts adapted to be coupled respectively to a chair seat/back assembly and to a chair base, said parts being pivoted together for movement with respect to one another about a pivot axis to permit tilting of the seat/back assembly with respect to the base in use; 
 a compression spring extending between respective spring seats carried by said upper and lower housing parts so as to normally maintain said parts in a rest position, while being compressed when the upper housing part tilts with respect to the lower housing part in use; and, 
 a spring tension control including wedge means between one of said spring seats and the associated housing part, said wedge means including a first wedge component coupled to one of said spring seats and said associated housing part and a pair of second wedge components co-operating with said first wedge component, said second wedge components being supported for lateral displacement towards and away from one another, the respective wedge components having co-operating sliding surfaces angled so that displacement of the second wedge components towards one another compresses the spring, increasing spring tension, while displacement of said moveable components away from one another allows the spring to relax, reducing spring tension, said second wedge components having a position of maximum spacing from one another in which the spring is fully relaxed and the overall length of the spring is less than the spacing between said spring seats for facilitating installation or removal of the spring; and an operator controlled actuator for effecting said displacement of the second wedge components towards and away from one another. 
 
   
   
     2. A tilt mechanism as claimed in  claim 1 , further comprising:
 stop means disposed between said upper and lower housing parts and defining said rest position of those parts, said stop means having a plurality of stop surfaces and being moveable to bring different ones of said surfaces selectively into an operative position between the housing parts, said stop surfaces defining respectively different angular positions of the housing parts with respect to one another; and, 
 an operator controlled actuator for moving said stop means. 
 
   
   
     3. A tilt mechanism as claimed in  claim 2 , wherein the stop means comprises a rotary stop with stop surfaces at different radial positions with respect to an axis about which the stop can be turned. 
   
   
     4. A tilt mechanism as claimed in  claim 3 , wherein said rotary stop comprises a rotary shaft that extends transversely of the upper and lower housing parts and a pair of rotary cam-like structures carried by the shaft and disposed one at each side of the tilt mechanism, the shaft projecting laterally of the mechanism for turning the cam-like structures, the shaft comprising said operator controlled actuator. 
   
   
     5. A tilt mechanism as claimed in  claim 4 , wherein the shaft is carried by the upper housing part and the cam-like structures rest on respective stop surfaces on the lower part. 
   
   
     6. A tilt mechanism as claimed in  claim 1 , wherein a second said compression spring is provided, the two springs being substantially identical and extending parallel to one another between the respective spring seats. 
   
   
     7. A tilt mechanism as claimed in  claim 1 , wherein said spring tension control extends between an end wall of the lower housing part and said one spring seat, the first wedge component being coupled to said one spring seat. 
   
   
     8. A tilt mechanism as claimed in  claim 7 , wherein said co-operating sliding surfaces each comprise a groove in one said surface having side walls between which the other co-operating sliding surfaces received. 
   
   
     9. A tilt mechanism as claimed in  claim 1 , further comprising:
 anti kick-back control means comprising a tongue carried by one of said housing parts and a rack carried by the other of said housing parts and having a plurality of teeth for receiving the tongue, the rack and tongue moving relative to one another as the housing parts pivot with respect to one another so that the tongue can engage different ones of said teeth corresponding to a series of different tilt positions of the housing parts with respect to one another, the rack being curved about said pivot axis; a slide supporting said tongue for longitudinal sliding movement between extended and retracted positions with respect to said rack, a tension spring connected between said tongue and slide, the tension spring being stretched for biasing said tongue to its extended position, and a tension member for retracting said tongue under operator control against the bias of the tension spring to permit said tilt position to be changed; 
 said compression spring providing a biasing force between said housing parts that causes the tongue to bind in the rack and prevent retraction of the tongue until a force counter to the biasing force is applied between the housing parts. 
 
   
   
     10. A tilt mechanism as claimed in  claim 9 , wherein the tension member extends between said tongue and an actuating member that is moveable towards and away from the rack for moving the tongue between its extended and retracted positions and wherein the tilt mechanism further comprises a pair of resilient jaws engaging said actuating member and defining respective detent positions for the actuating member corresponding to said extended and retracted positions of the tongue.